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mptcp: depends on IPV6 but not as a module
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Like TCP, MPTCP cannot be compiled as a module. Obviously, MPTCP IPv6'
support also depends on CONFIG_IPV6. But not all functions from IPv6
code are exported.

To simplify the code and reduce modifications outside MPTCP, it was
decided from the beginning to support MPTCP with IPv6 only if
CONFIG_IPV6 was built inlined. That's also why CONFIG_MPTCP_IPV6 was
created. More modifications are needed to support CONFIG_IPV6=m.

Even if it was not explicit, until recently, we were forcing CONFIG_IPV6
to be built-in because we had "select IPV6" in Kconfig. Now that we have
"depends on IPV6", we have to explicitly set "IPV6=y" to force
CONFIG_IPV6 not to be built as a module.

In other words, we can now only have CONFIG_MPTCP_IPV6=y if
CONFIG_IPV6=y.

Note that the new dependency might hide the fact IPv6 is not supported
in MPTCP even if we have CONFIG_IPV6=m. But selecting IPV6 like we did
before was forcing it to be built-in while it was maybe not what the
user wants.

Reported-by: Geert Uytterhoeven <[email protected]>
Fixes: 010b430 ("mptcp: MPTCP_IPV6 should depend on IPV6 instead of selecting it")
Signed-off-by: Matthieu Baerts <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
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matttbe authored and kuba-moo committed Oct 21, 2020
1 parent 05f90bf commit 0ed37ac
Showing 1 changed file with 1 addition and 1 deletion.
2 changes: 1 addition & 1 deletion net/mptcp/Kconfig
Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,7 @@ config INET_MPTCP_DIAG

config MPTCP_IPV6
bool "MPTCP: IPv6 support for Multipath TCP"
depends on IPV6
depends on IPV6=y
default y

config MPTCP_KUNIT_TESTS
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